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Rotating magnetic fields by SigmaDelta on 03 Aug, 2019 22:22
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Hi,
I've been interested in reactionless propulsion for a long time now, and one concept that seems to crop up a lot is rotating magnetic fields.
Whether it's Searl, Podkletnov, the Marcus device , it seems to be a recurring concept that (perhaps) a rotating magnetic field (particularly one that is rotating very fast or uses superconductors) *may* be able to affect the space-time fabric and hence create a reactionless force.
I'm a rational guy and I don't have much time for the pseudoscience, but I think we have to keep an open mind.
So I was wondering what you folks thought about this as a propulsion concept, are you aware of any recent experiments, have you done any experiments yourself, does this have potential.
Very interested to hear any replies,
Thank you. -
#1 by dustinthewind on 06 Aug, 2019 13:21
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I did an experiment myself where we rotated a magnetic field symmetrically about it's axis. By vxB=E there should be a change in charge. We built a very low capacitance capacitor using just aluminum sheeting and styrofoam. the capacitance was so low the wood I tried to mount it on allow the charge to drain straight through the wood. The capacitor what is a large aluminum double ring. It had to be mounted on styrofoam and placed around the solenoid, or a magnet that I put on a Dremel. They're very high Resistance voltmeter had to be used. The drain time could be observed by using a static-charged wand. You could see yourself jump in the room because of the change in charge. Powering up the solenoid actually induced a repulsive effect on the capacitor but that wasn't rotating. Actual rotation of the solenoid didn't seem to induce the expected EMF or apparent change in charge of the solenoid. It's suggested that the symmetric B field lines wouldn't rotate.
I came to the conclusion later that changing magnetic fields radiate. That is information travels about the magnetic field at the speed of light away from the source. magnetic field lines that were over a certain distance and angularly rotating could eventually exceed the speed of light.
Pulsar stars are known to be magnetic but wobble. They radiate mainly along the axis of their magnetic field because the the axis wobbling induces the greatest change in the magnetic field.
a three phase motor is another example of where you can create what looks like a rotating magnetic field. However the 3-phase coils radiation are what induce the counter currents in the central shaft. Essentially induction being determined by the change in the rate of information.
The only time I would suspect that a magnetic field could actually rotate would be in a lens-thirring effect where space-time itself is rotating. That is space-time itself determines the non-rotating frame. Around large rotating objects that drag space-time around with them space-time rotates slightly. However at larger distances this drops back to non-rotating with respect to the rest of the universe. That is the presence of local matter and non-local matter determining the frame of space-time.
That is existing and rotating with rotating space-time one does not experience centrifugal force. They should also not observe them selves as rotating with respect to the magnetic field even though with different distance from the source, non-locally, the magnetic field rotates with the space time.
I was speculating however that if curved space-time can induce acceleration on particles then asymmetrically accelerating particles might have a small effect on the local curvature of space time. If you do this in a cavity you can induce cycles of asymmetric acceleration. The Lorentz factor seems to be geometric and suggests a vector of length c rotating with respect local space time where the vector v points left and right. The time vector shortens as the c vector rotates. The Lorentz factor changes ones effective mass also. Gravity is represented by a curved line. We on earth have our vector rotated with respect to local space time giving us an effective velocity and slowing our time.
At the event horizon of a black hole the line becomes vertical. The time axis points up and the space axis is left and right. The local space-time in a gravity well rotates into the time vector and its time rotates into the space vector. This gives the illusion of a flow of space time.
They mention that in this video also at one point. Don't have the time to find it but its later in the video.
https://www.worldsciencefestival.com/videos/black-holes-and-holographic-worlds/?gclid=EAIaIQobChMIqpGbxc6I4gIVDZ-fCh1_8gbpEAAYASAAEgLWC_D_BwE
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#2 by Bob012345 on 06 Aug, 2019 18:17
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Hi,
I've been interested in reactionless propulsion for a long time now, and one concept that seems to crop up a lot is rotating magnetic fields.
Whether it's Searl, Podkletnov, the Marcus device , it seems to be a recurring concept that (perhaps) a rotating magnetic field (particularly one that is rotating very fast or uses superconductors) *may* be able to affect the space-time fabric and hence create a reactionless force.
I'm a rational guy and I don't have much time for the pseudoscience, but I think we have to keep an open mind.
So I was wondering what you folks thought about this as a propulsion concept, are you aware of any recent experiments, have you done any experiments yourself, does this have potential.
Very interested to hear any replies,
Thank you.
One thing's for sure is that there is a lot of nonsense out there! What people do discuss is the possibility of propellentless propulsion. There is no such thing as a reactionless force with the caveat that is is possible to use the finite speed of light to force the action and reaction out of phase so they add instead of subtract on a system. Most people say that such a device simply amounts to an inefficient photon rocket. There are two basic concepts considered still "in the running" but are highly controversial and most people are skeptical. One is devices based on the Woodward Effect and the other are various forms of the EmDrive. Both are active subjects of intense ongoing experimentation. -
#3 by meberbs on 06 Aug, 2019 19:31
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I did an experiment myself where we rotated a magnetic field symmetrically about it's axis. By vxB=E there should be a change in charge.
That equation is wrong (cross product of velocity and magnetic field is proportional to force due to magnetic field, it doesn't generate and E field.) Even if you had the correct equation, your statement is based on a complete misunderstanding. Rotating a magnet around its axis of symmetry does not generally result in a changing magnetic field, so the effect you were looking for was never actually expected to exist to begin with.I came to the conclusion later that changing magnetic fields radiate. That is information travels about the magnetic field at the speed of light away from the source.
This is a conclusion you could find in any electrodynamics textbook. Accelerating charges radiate. Changing magnetic fields generally imply accelerating charges (caveats exist related to things like constant velocity magnets) Information about accelerating charges propagates at the speed of light along with the electromagnetic radiation.magnetic field lines that were over a certain distance and angularly rotating could eventually exceed the speed of light.
Clearly incorrect conclusion since as stated just previously, everything involved propagates at the speed of light. It seems like here you are considering something similar to how a shadow can move at a high apparent speed, because it does not represent anything physically moving. The information conveyed by the shadow actually propagates at the speed of light from the source, and there is nothing strange about it arriving at 2 different, distant and widely separated points at a similar time.
A lot of the rest of your post that I didn't respond to basically seems to be you putting different concepts together in a very non-rigorous fashion that doesn't make any sense if you were to try to explain it rigorously. It demonstrates a lack of understanding of the concepts you are talking about, or even what the terms you are using mean.
This manner of throwing things together is similar to some of the things referenced by SigmaDelta. It sure sounds fancy to throw around words like "rotating magnets" while talking about space-time, but it doesn't necessarily mean anything. Most scientist simply ignore such concepts, because they aren't even remotely plausible to the point where it seems like there isn't even a coherent way to state them.
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#4 by SigmaDelta on 07 Aug, 2019 00:00
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Thanks for the replies,
I apologise in advance if this is silly science, but I came across a Dr. John Brandenburg, who claims that gravity is linked to electromagnetism via radiation pressure and the Poynting vector.
This video pretty much explains it:
I think the proposed reason why you need a rotating magnetic field rather than a static one is because this sustains the presence of the radiation pressure, with a static field the radiation pressure is only temporary. -
#5 by meberbs on 07 Aug, 2019 00:50
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Thanks for the replies,
He immediately discredits himself by claiming that radiation pressure is different than electric and magnetic forces. If you take the electric and magnetic fields of an electromagnetic wave, and calculate the force they exert on a charge (or a metal plate, etc.) you exactly get radiation pressure. It makes no sense whatsoever to count it as a separate force, you would be double counting.
I apologise in advance if this is silly science, but I came across a Dr. John Brandenburg, who claims that gravity is linked to electromagnetism via radiation pressure and the Poynting vector.
He doesn't do himself any favors when he references Crookes Radiometer, which actually operates by heat transfer with the low pressure gas in the bulb. It spins the wrong way to be explained by radiation pressure. You would need a much higher vacuum to be able to detect the very small radiation pressure effect.
By the time he starts explaining the gravity connection he has stopped making any sense at all. Radiation pressure is nothing like gravity at all, since gravity applies a force directly proportional to the mass of the object, whereas, the mass is irrelevant to radiation pressure, and only the effective cross sectional area of the object and the power per area of the incident electrodynamic wave is relevant. I stopped listening halfway through, but you can't explain the amount of force from gravity, the scaling with distance, or proportion to mass with the "external radiation pressure from some nonsense version of zero point energy pushing things inwards." It simply is incoherent and illogical. -
#6 by dustinthewind on 07 Aug, 2019 01:03
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sigh, it is not wrong.I did an experiment myself where we rotated a magnetic field symmetrically about it's axis. By vxB=E there should be a change in charge.
That equation is wrong (cross product of velocity and magnetic field is proportional to force due to magnetic field, it doesn't generate and E field.) Even if you had the correct equation, your statement is based on a complete misunderstanding. Rotating a magnet around its axis of symmetry does not generally result in a changing magnetic field, so the effect you were looking for was never actually expected to exist to begin with.
https://en.wikipedia.org/wiki/Lorentz_force
a charge observing such an E field feels a force q*E=q*(v x B) = F. It's an apparent change in charge all the charges would observe if the magnetic field lines you draw to represent the magnetic field actually rotated axially. They do not.
Go ahead and try it. imagine the field lines having velocity. fingers forward are v. Bend the fingers in to represent B. The E field is in the direction of the thumb. now move the hand around the cylindrical capacitor and the E field rotates away from the solenoid - if the B field lines actually rotated.
Obviously Barnett considered the experiment worth doing himself.
http://physics.princeton.edu/~mcdonald/examples/barnett.pdf
He shielded his in the lab frame and if an electric field were to be observed in the lab frame I didn't think he would see it, because the shield in the lab frame would react to shield, but that was my opinion.QuoteI came to the conclusion later that changing magnetic fields radiate. That is information travels about the magnetic field at the speed of light away from the source.
This is a conclusion you could find in any electrodynamics textbook. Accelerating charges radiate. Changing magnetic fields generally imply accelerating charges (caveats exist related to things like constant velocity magnets) Information about accelerating charges propagates at the speed of light along with the electromagnetic radiation.magnetic field lines that were over a certain distance and angularly rotating could eventually exceed the speed of light.
Clearly incorrect conclusion since as stated just previously, everything involved propagates at the speed of light. It seems like here you are considering something similar to how a shadow can move at a high apparent speed, because it does not represent anything physically moving. The information conveyed by the shadow actually propagates at the speed of light from the source, and there is nothing strange about it arriving at 2 different, distant and widely separated points at a similar time.
A lot of the rest of your post that I didn't respond to basically seems to be you putting different concepts together in a very non-rigorous fashion that doesn't make any sense if you were to try to explain it rigorously. It demonstrates a lack of understanding of the concepts you are talking about, or even what the terms you are using mean.
This manner of throwing things together is similar to some of the things referenced by SigmaDelta. It sure sounds fancy to throw around words like "rotating magnets" while talking about space-time, but it doesn't necessarily mean anything. Most scientist simply ignore such concepts, because they aren't even remotely plausible to the point where it seems like there isn't even a coherent way to state them.
The B field is not a shadow to some one that thinks of the field as a structure. That's the point if your going to ask yourself if the magnetic field can rotate or not. It's actually a common misconception that it does rotate.
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#7 by 1 on 07 Aug, 2019 03:14
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sigh, it is not wrong.
Yes, it is; the most basic reason being you've neglected the force term in your previous equation. If you're going to rearrange the equation, you've got two options:
qE = F - q(VxB) or
q(VxB) = F - qE
Either option may have situational use, but neither has intrinsic value. Read a bit further down in your wiki link:QuoteThe force F acting on a particle of electric charge q with instantaneous velocity v, due to an external electric field E and magnetic field B,
Bold mine. 'External' means E and B fields exist (or don't exist) completely independently of anything else that's happening. Either field can take on any value, including zero, without any impact on the other. Changing the steady-state magnitude of either field can influence the force experienced by a charged particle, but will never change the value of the other field. Nor can it somehow alter the amount of charge in your test fixture, and vice versa.
qE = q(VxB) = F has no meaning.
I can't really tell what you've done with your test setup, but it sounds like you might have (sort of) replicated step 2 of the Faraday Paradox. See below:
https://en.wikipedia.org/wiki/Faraday_paradox#The_procedure
Of course, as usually the case with well-developed theories, there doesn't actually exist any paradox; only misapplication of the theory itself.The B field is not a shadow to some one that thinks of the field as a structure.
The point of the shadow analogy isn't to illustrate the the field has no structure, but to illustrate the fact that the apparent motion of the field has no meaning, because no part of the field is actually traveling in that superluminal direction. This is a simple variation of the Lighthouse paradox.
Think of it this way instead. Go outside, and look up at the stars. Now, start spinning in circles.
You should now "see" a bunch of stars circling you at very superluminal velocities. Of course, they're not actually doing anything of the sort. You're simply moving your field of view across the sky. In addition to your field of view, you could cast a beam light (or shadow) of your own on any number of stars as rapidly as you wish. Eventually. It'll still take many, many years for that beam to arrive, no matter how fast you sweep your hand across the sky. -
#8 by Bob012345 on 07 Aug, 2019 17:39
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Thanks for the replies,
He immediately discredits himself by claiming that radiation pressure is different than electric and magnetic forces. If you take the electric and magnetic fields of an electromagnetic wave, and calculate the force they exert on a charge (or a metal plate, etc.) you exactly get radiation pressure. It makes no sense whatsoever to count it as a separate force, you would be double counting.
I apologise in advance if this is silly science, but I came across a Dr. John Brandenburg, who claims that gravity is linked to electromagnetism via radiation pressure and the Poynting vector.
Just to clarify, are you are saying Lorentz forces are exactly and always the radiation pressure of photons? Or do you mean only when in the form of propagating EM waves? Thanks. -
#9 by meberbs on 07 Aug, 2019 18:04
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The second one, the forces due to propagating EM waves can be determined purely from the fields and the charges they act on. Magnetic fields can exist in steady state with no propagating EM waves, and still result in Lorentz forces. (Virtual photons and related quantum mechanical descriptions of such things are beyond the scope of what is relevant for what I was saying.)Thanks for the replies,
He immediately discredits himself by claiming that radiation pressure is different than electric and magnetic forces. If you take the electric and magnetic fields of an electromagnetic wave, and calculate the force they exert on a charge (or a metal plate, etc.) you exactly get radiation pressure. It makes no sense whatsoever to count it as a separate force, you would be double counting.
I apologise in advance if this is silly science, but I came across a Dr. John Brandenburg, who claims that gravity is linked to electromagnetism via radiation pressure and the Poynting vector.
Just to clarify, are you are saying Lorentz forces are exactly and always the radiation pressure of photons? Or do you mean only when in the form of propagating EM waves? Thanks. -
#10 by Bob012345 on 07 Aug, 2019 18:13
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The second one, the forces due to propagating EM waves can be determined purely from the fields and the charges they act on. Magnetic fields can exist in steady state with no propagating EM waves, and still result in Lorentz forces. (Virtual photons and related quantum mechanical descriptions of such things are beyond the scope of what is relevant for what I was saying.)Thanks for the replies,
He immediately discredits himself by claiming that radiation pressure is different than electric and magnetic forces. If you take the electric and magnetic fields of an electromagnetic wave, and calculate the force they exert on a charge (or a metal plate, etc.) you exactly get radiation pressure. It makes no sense whatsoever to count it as a separate force, you would be double counting.
I apologise in advance if this is silly science, but I came across a Dr. John Brandenburg, who claims that gravity is linked to electromagnetism via radiation pressure and the Poynting vector.
Just to clarify, are you are saying Lorentz forces are exactly and always the radiation pressure of photons? Or do you mean only when in the form of propagating EM waves? Thanks.
Thanks. But would you expect the same instantaneous Lorentz force on a charge or current carrying wire whether the source of the B field is a wave or a steady state situation if at that moment the B field is the same? -
#11 by meberbs on 07 Aug, 2019 21:27
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Thanks. But would you expect the same instantaneous Lorentz force on a charge or current carrying wire whether the source of the B field is a wave or a steady state situation if at that moment the B field is the same?
All else being equal then the force would be the same. (All else includes the same instantaneous velocity of the charge(s) and the same instantaneous electric field.) -
#12 by dustinthewind on 08 Aug, 2019 06:51
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We were discussing only the B field - hence vxB=E not E+vxB=E. The E field from the B field is a separate entity as that of a charge's, what I call its "non-relativistic electric field". I don't disagree there. Electric field pancaking and what I call electric field tilting is an effect of a charges B field. Summed together they make the fully relativistic electric field E+vxB=E_full that is the sum of what tilts, pancakes, and the classical electric field.sigh, it is not wrong.
Yes, it is; the most basic reason being you've neglected the force term in your previous equation. If you're going to rearrange the equation, you've got two options:
qE = F - q(VxB) or
q(VxB) = F - qE
Either option may have situational use, but neither has intrinsic value. Read a bit further down in your wiki link:QuoteThe force F acting on a particle of electric charge q with instantaneous velocity v, due to an external electric field E and magnetic field B,
Bold mine. 'External' means E and B fields exist (or don't exist) completely independently of anything else that's happening. Either field can take on any value, including zero, without any impact on the other. Changing the steady-state magnitude of either field can influence the force experienced by a charged particle, but will never change the value of the other field. Nor can it somehow alter the amount of charge in your test fixture, and vice versa.
qE = q(VxB) = F has no meaning.
There seems to be some confustion at suggesting that a concentric ring capacitor such as Barnett and my team use, was used to observe an "effective change in charge". In fact when the capacitor is spun in the magnetic field it does observe an effective change in charge from the source of the magnetic field, let that sink in - yet when the magnet is spun no change in charge. (A magnetic effective change in charge not a classical change in charge - a charges presence is measured by its electric field so they can be hard to tell apart.)In fact it was shown that so long as a current loop is used to measure induced EMFs from the motion of the disk and magnet it is not possible to tell if the magnetic field does or does not rotate with the magnet.
The above reason is why Barnett and my team used a capacitor. If you use a close circuit you can't tell, but you can tell if you use an open circuit. A capacitor.
A homopolar motor works because the rotating metal thinks it sees an E field all around the disk, but the non-roating wire does not see such an E field. This E field is entirely from the B field, not a static charge, but appears as a change in charge as observed from a large rotating structure, such as the concentric ring capacitor. This is because different parts of the capacitor have different velocity vectors, so each charge in the capacitor observes a different dipole electric field from the solenoid, which is a magnetic effect.Quote
Yes, others have come to the same conclusions, and uncovering reality from different viewpoints tends to lead people to the same conclusions.
I can't really tell what you've done with your test setup, but it sounds like you might have (sort of) replicated step 2 of the Faraday Paradox. See below:
https://en.wikipedia.org/wiki/Faraday_paradox#The_procedure
Of course, as usually the case with well-developed theories, there doesn't actually exist any paradox; only misapplication of the theory itself.Quote from: =https://en.wikipedia.org/wiki/Faraday_paradox#The_procedureSeveral experiments have been proposed using electrostatic measurements or electron beams to resolve the issue, but apparently none have been successfully performed to date.[citation needed]
We didn't need an electron beam to test the concept but rather an open circuit capacitor.Quote
If the B field radiates to deposit over space, becuse new information about the B field doesn't travel faster than light then changes in the B field propagate at the speed of light. Light and Shadow are bedfellows. Goes togther like a horse and carriage ;o) TV show quote from an old sitcom. It illustrates the importance to see the magnetic field not as a structure but as a propagating entity - defined by local space-time.The B field is not a shadow to some one that thinks of the field as a structure.
The point of the shadow analogy isn't to illustrate the the field has no structure, but to illustrate the fact that the apparent motion of the field has no meaning, because no part of the field is actually traveling in that superluminal direction. This is a simple variation of the Lighthouse paradox.
Think of it this way instead. Go outside, and look up at the stars. Now, start spinning in circles.
You should now "see" a bunch of stars circling you at very superluminal velocities. Of course, they're not actually doing anything of the sort. You're simply moving your field of view across the sky. In addition to your field of view, you could cast a beam light (or shadow) of your own on any number of stars as rapidly as you wish. Eventually. It'll still take many, many years for that beam to arrive, no matter how fast you sweep your hand across the sky.If you hold the view that the field flux is a physical entity, it does rotate ...
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#13 by meberbs on 08 Aug, 2019 14:54
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We were discussing only the B field - hence vxB=E not E+vxB=E. The E field from the B field is a separate entity as that of a charge's, what I call its "non-relativistic electric field". I don't disagree there.
Can you see the difference between the letter "E", and the letter "F"? Let me repeat that in lower case (although lower case variables normally would mean something different.) The difference between the letter "e" and the letter "f"
The equation you just wrote is nonsensical. You have the same variable E on both sides, so just subtract it off and you are left with v x B = 0. This is only true in the special cases that v = 0, B = 0, or v and B are parallel. The correct equation, (using lower case for e and f, since you failed to read it correctly in the previous post, or in the links provided, is f = q*e +q* (vxB) The magnetic field directly generates a force, it doesn't generate some pseudo E-field to do its work for it. That wouldn't even make sense.
When you are saying you "don't disagree," you are actually saying that you understood nothing of 1's post, because 1 stated that the E field and B field are completely separate and unrelated in this (quasi-static) case. You are saying that the B -field generates an E-Field, and you are claiming so in a fundamentally inconsistent way. (In non-quasi-static cases, it is changing B fields that generate an E-Field, but before I try to explain what these words mean, you need to recognize the algebraic mistakes you are making.)
With that said, it doesn't sound like you understood a single word of 1's post. Hopefully now that I cleared up what seems to be some confusion with variables on your part, you will understand it better, so go back and re-read 1's post again, At least until you comprehend the fact that your equations are completely wrong, and any prediction that spinning a magnet on its axis of symmetry should do anything is a complete misapplication of the theory, and that is over a century old news. -
#14 by dustinthewind on 08 Aug, 2019 20:44
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I think the problem is rather your desire to see a lack of understanding. It was already made clear in the rest of the text it was understood E_q+vxB=E_full such that E_q is not the same as E_full. Maybe it was lazy to lack the annotation at that point but the rest of the text makes it clear.We were discussing only the B field - hence vxB=E not E+vxB=E. The E field from the B field is a separate entity as that of a charge's, what I call its "non-relativistic electric field". I don't disagree there.
Can you see the difference between the letter "E", and the letter "F"? Let me repeat that in lower case (although lower case variables normally would mean something different.) The difference between the letter "e" and the letter "f"
The equation you just wrote is nonsensical. You have the same variable E on both sides, so just subtract it off and you are left with v x B = 0. This is only true in the special cases that v = 0, B = 0, or v and B are parallel. The correct equation, (using lower case for e and f, since you failed to read it correctly in the previous post, or in the links provided, is f = q*e +q* (vxB) The magnetic field directly generates a force, it doesn't generate some pseudo E-field to do its work for it. That wouldn't even make sense.
When you are saying you "don't disagree," you are actually saying that you understood nothing of 1's post, because 1 stated that the E field and B field are completely separate and unrelated in this (quasi-static) case. You are saying that the B -field generates an E-Field, and you are claiming so in a fundamentally inconsistent way. (In non-quasi-static cases, it is changing B fields that generate an E-Field, but before I try to explain what these words mean, you need to recognize the algebraic mistakes you are making.)
With that said, it doesn't sound like you understood a single word of 1's post. Hopefully now that I cleared up what seems to be some confusion with variables on your part, you will understand it better, so go back and re-read 1's post again, At least until you comprehend the fact that your equations are completely wrong, and any prediction that spinning a magnet on its axis of symmetry should do anything is a complete misapplication of the theory, and that is over a century old news.
Yes an electron moving relative to a magnetic source does observe an E field in it's moving frame and the reason for the force. The magnetic field being a velocity dependent dipole electric field. -
#15 by meberbs on 08 Aug, 2019 21:35
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I think the problem is rather your desire to see a lack of understanding. It was already made clear in the rest of the text it was understood E_q+vxB=E_full such that E_q is not the same as E_full. Maybe it was lazy to lack the annotation at that point but the rest of the text makes it clear.
No, your equation is simply 100% wrong with or without the annotation. There is only one E field. There is no additional E field that is proportional to the velocity of the charge that is moving in a magnetic field.
Yes an electron moving relative to a magnetic source does observe an E field in it's moving frame and the reason for the force. The magnetic field being a velocity dependent dipole electric field.
You now are starting to talk about different reference frames, and conflating the results from different reference frames, which is a great way to get incorrect answers. Electromagnetic fields in special relativity transform between reference frames as a tensor, where the tensor is a function of both the electric and magnetic fields in each frame. Before trying to discuss different reference frames, first you need to understand how electrodynamics works in a single frame.
Also, please don't make false ad hominem attacks like claiming that I desire to see a lack of understanding. What I actually desire is for you to understand. -
#16 by 1 on 08 Aug, 2019 22:00
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We were discussing only the B field - hence vxB=E not E+vxB=E.
If we're only discussing the B field, then your equation shouldn't have E anywhere in it. And you're still neglecting the force term. This is the third time this has been pointed out to you. If you're not going to address that, then this entire discussion should be terminated....what I call...
Stop doing this. If you want to have any meaningful discussion, you need to apply proper terminology in your posts. "Tilting" and "pancaking" fields have no meaning to anyone else. "Non-relativistic electric field" is also poorly defined, as all fields can be made relativistic by simply changing reference frames. It sounds like you're trying to declare a rest-frame field of something, but it's very unclear of what.In fact when the capacitor is spun in the magnetic field it does observe an effective change in charge from the source of the magnetic field, let that sink in - yet when the magnet is spun no change in charge.
Let what sink in? The wiki page perfectly resolves the difference between the two scenarios. There's nothing unexpected here. I suspect this might be one of your fundamental roadblocks. Capacitors don't "change" charge; they displace charge. Electrons are moved such that one plate has more negative charge than positive, and the other has more positive charge than negative. The magnitude of this displacement is what's given/used in capacitor formulae. The net charge over the entire device can almost always be considered to be zero.This E field is entirely from the B field, not a static charge, but appears as a change in charge as observed from a large rotating structure, such as the concentric ring capacitor. This is because different parts of the capacitor have different velocity vectors, so each charge in the capacitor observes a different dipole electric field from the solenoid, which is a magnetic effect.
No. If you're switching reference frames, an external B field in one reference frame manifests as external E and B fields in another. This is precisely the kind of field you were trying to ignore in the beginning of your post. This is why I stressed that the E and B fields can take on arbitrary values.
In a more rigorous E&M treatment of your setup, where the exact cause of the creation your B field would be considered, then you might be able calculate some sort of charge-based effect at a distance. But if you're going to start your calculations at a place where the B field is simply already there and you don't really care why (which is fine for many applications), then the creation of an E field due to switching reference frames needs to be treated the same way. It's simply, "just there". There is no change in charge, and certainly not a local one.If the B field radiates to deposit over space, becuse new information about the B field doesn't travel faster than light then changes in the B field propagate at the speed of light.
B fields by themselves don't have radiating or propagating solutions, but otherwise this is fine.Light and Shadow are bedfellows.
Of course they are. Just as is the idea that rotating field lines can exceed the speed of light. It has no physical meaning. -
#17 by Bob012345 on 08 Aug, 2019 23:58
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I think the problem is rather your desire to see a lack of understanding. It was already made clear in the rest of the text it was understood E_q+vxB=E_full such that E_q is not the same as E_full. Maybe it was lazy to lack the annotation at that point but the rest of the text makes it clear.
No, your equation is simply 100% wrong with or without the annotation. There is only one E field. There is no additional E field that is proportional to the velocity of the charge that is moving in a magnetic field.
Yes an electron moving relative to a magnetic source does observe an E field in it's moving frame and the reason for the force. The magnetic field being a velocity dependent dipole electric field.
You now are starting to talk about different reference frames, and conflating the results from different reference frames, which is a great way to get incorrect answers. Electromagnetic fields in special relativity transform between reference frames as a tensor, where the tensor is a function of both the electric and magnetic fields in each frame. Before trying to discuss different reference frames, first you need to understand how electrodynamics works in a single frame.
Also, please don't make false ad hominem attacks like claiming that I desire to see a lack of understanding. What I actually desire is for you to understand.
Here is a good source for transformations of fields between reference frames.
http://www.feynmanlectures.caltech.edu/II_26.html
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#18 by dustinthewind on 10 Aug, 2019 01:04
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Having only a B field means you can neglect E in E+vxB=E_full. Force is just taking the equation times q the charge. Go ahead put a q in there if it suits you.We were discussing only the B field - hence vxB=E not E+vxB=E.
If we're only discussing the B field, then your equation shouldn't have E anywhere in it. And you're still neglecting the force term. This is the third time this has been pointed out to you. If you're not going to address that, then this entire discussion should be terminated.Quote
Pancaking is Edward Purcells terminology from his book electricity and magnetism. It describes the relativistic effect if you imagine a ball of dough and you smash it so it forms an oval....what I call...
Stop doing this. If you want to have any meaningful discussion, you need to apply proper terminology in your posts. "Tilting" and "pancaking" fields have no meaning to anyone else. "Non-relativistic electric field" is also poorly defined, as all fields can be made relativistic by simply changing reference frames. It sounds like you're trying to declare a rest-frame field of something, but it's very unclear of what.
http://physics.weber.edu/schroeder/mrr/mrrtalk.html
Electric field tilting is what I call it when you have multiple vectors involved which tilt the pancaked electric field.
You can make an electric field of a charge relativistic by first taking its classical electric field (spherical) and by it having velocity, it now has a magnetic field. You then take your relative velocity w.r.t. its magnetic field and this gives its relativistic, pancaked electric field. In escence the magnetic field is the relativistic part of the electric field. So the magnetic field not rotating is an artifact of the electric field not rotating.
Light coming from the B field is akin to light coming from the relativistic part of the electric field.Quote
Right, but a capacitor will charge if it experiences a local change in charge or net change in electric flux through its surface. The charge in it reacts to the presence of the electric field. So if it appears to the capacitor that there is an electric field coming from the solenoid it will react to this electric field. If you spin the capacitor this happens. Both capacitor plates don't change in charge as a sum but each individual plate experience a voltage that will change their charge individually in the presence of an external electric field, or induce a voltage if the charge can't flow.In fact when the capacitor is spun in the magnetic field it does observe an effective change in charge from the source of the magnetic field, let that sink in - yet when the magnet is spun no change in charge.
Let what sink in? The wiki page perfectly resolves the difference between the two scenarios. There's nothing unexpected here. I suspect this might be one of your fundamental roadblocks. Capacitors don't "change" charge; they displace charge. Electrons are moved such that one plate has more negative charge than positive, and the other has more positive charge than negative. The magnitude of this displacement is what's given/used in capacitor formulae. The net charge over the entire device can almost always be considered to be zero.Quote
The experiment starts with a B field in the lab frame and only a B field in the lab frame. If you assume it rotates axially you have to transform it into an E field in the lab frame which is that transformation. It's already known E and B fields can transform. This is located a few paragraphs above discussing how you get pancaked electric fields.This E field is entirely from the B field, not a static charge, but appears as a change in charge as observed from a large rotating structure, such as the concentric ring capacitor. This is because different parts of the capacitor have different velocity vectors, so each charge in the capacitor observes a different dipole electric field from the solenoid, which is a magnetic effect.
No. If you're switching reference frames, an external B field in one reference frame manifests as external E and B fields in another. This is precisely the kind of field you were trying to ignore in the beginning of your post. This is why I stressed that the E and B fields can take on arbitrary values.Quote
The experiment starts with a B field from a solenoid in the center of a concentric ring capactor with very low capacitance. The B field was measured with a hall probe and predicted using finite element analysis.
In a more rigorous E&M treatment of your setup, where the exact cause of the creation your B field would be considered, then you might be able calculate some sort of charge-based effect at a distance. But if you're going to start your calculations at a place where the B field is simply already there and you don't really care why (which is fine for many applications), then the creation of an E field due to switching reference frames needs to be treated the same way. It's simply, "just there". There is no change in charge, and certainly not a local one.
The creation of an E field via each charge in the capacitors individual velocity vector through the magnetic field means they each see a different electric field, with a different vector. Summing that electric field up over the capacitor gives the net change in electric flux that the charges in the capacitor see as a whole. They will react to this change in flux, similar to a homopolar motor.QuoteIf the B field radiates to deposit over space, becuse new information about the B field doesn't travel faster than light then changes in the B field propagate at the speed of light.
B fields by themselves don't have radiating or propagating solutions, but otherwise this is fine.Light and Shadow are bedfellows.
Of course they are. Just as is the idea that rotating field lines can exceed the speed of light. It has no physical meaning. -
#19 by meberbs on 10 Aug, 2019 05:24
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Having only a B field means you can neglect E in E+vxB=E_full. Force is just taking the equation times q the charge. Go ahead put a q in there if it suits you.We were discussing only the B field - hence vxB=E not E+vxB=E.
If we're only discussing the B field, then your equation shouldn't have E anywhere in it. And you're still neglecting the force term. This is the third time this has been pointed out to you. If you're not going to address that, then this entire discussion should be terminated.
Putting a q in does not change the fact that there is no such thing as E_full. If there is no electric field, it means that there is no electric field, not that there is still some extra magic test particle dependent field that appears wherever you feel like. Please stop making things up. You referenced Purcell, so you should be able to look through his book and see that your equation is not a real electrodynamics equation.
As 1 stated, if you keep refusing to acknowledge basic facts like this, there is no point in having this conversation.The experiment starts with a B field in the lab frame and only a B field in the lab frame. If you assume it rotates axially you have to transform it into an E field in the lab frame which is that transformation. It's already known E and B fields can transform. This is located a few paragraphs above discussing how you get pancaked electric fields.
E and B fields transform when you change reference frames. Spinning a magnet around its axis of symmetry is not a frame transformation. Your phrase "if you assume it rotates axially" in this context literally has no meaning. spinning the magnet does not change the fields. The fields at every point remain the same, so it is meaningless to describe them as spinning. It is no different than saying a nonsensical statement like "if you assume the sky tastes pink," you are trying to apply a concept that simply doesn't apply, and any related statements you make lose any meaning as well.
